linux tty 串口驱动

linux tty 串口驱动

TTY和serial port

tty:描述各类终端设备，主要包括tty核心、tty线路规划、tty驱动。tty核心是对整个tty设备的抽象，对用户空间提供统一的接口；tty线路规划是对传输数据的格式化，tty驱动则是面向tty设备的硬件驱动。
serial port也是tty的一种，主要负责对串口硬件的驱动

  • 串口驱动结构如下图所示：

tty&serial port

核心数据结构

  • uart_driver

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    struct uart_driver{
      struct module *owner;
      const char *driver_name;
      const char *dev_name;
      int major;
      int minor;
      int nr;       //uart_driver支持的串口个数
      struct console *cons;

      /*以下两个成员不在初始化uart_driver时赋值*/
      struct uart_state *state;
      struct tty_driver *tty_driver;
    };
    • tty_driver与上层tty联系，会在register_uart_driver的过程中被赋值
    • uart_state中的uart_port成员是uart_driver中真正与硬件打交道的成员，在register_uart_driver的过程中为其分配内存

  • uart_state

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    struct uart_state {
      struct tty_port port;
      int pm_state;
      struct circ_buf xmit;
      struct tasklet_struct tlet;
      struct uart_port *uart_port;
    };
    • 此结构体中最重要的成员就是uart_port，在register时会根据uart_driver->nr成员的值去为uart_state分配内存，存放驱动支持的串口物理信息

  • uart_port

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    struct uart_port {
      spinlock_t             lock;           /* 串口端口锁 */
      unsigned int           iobase;         /* IO端口基地址 */
      unsigned char __iomem *membase;        /* IO内存基地址,经映射(如ioremap)后的IO内存虚拟基地址 */
      unsigned int           irq;            /* 中断号 */
      unsigned int           uartclk;        /* 串口时钟 */
      unsigned int           fifosize;       /* 串口FIFO缓冲大小 */
      unsigned char          x_char;         /* xon/xoff字符 */
      unsigned char          regshift;       /* 寄存器位移 */
      unsigned char          iotype;         /* IO访问方式 */
      unsigned char          unused1;

      #define UPIO_PORT        (0)               /* IO端口 */
      #define UPIO_HUB6        (1)
      #define UPIO_MEM         (2)               /* IO内存 */
      #define UPIO_MEM32       (3)
      #define UPIO_AU          (4)               /* Au1x00 type IO */
      #define UPIO_TSI         (5)               /* Tsi108/109 type IO */
      #define UPIO_DWAPB       (6)               /* DesignWare APB UART */
      #define UPIO_RM9000      (7)               /* RM9000 type IO */

      unsigned int        read_status_mask;  /* 关心的Rx error status */
      unsigned int        ignore_status_mask;/* 忽略的Rx error status */
      struct uart_info      *info;           /* pointer to parent info */
      struct uart_icount     icount;         /* 计数器 */

      struct console        *cons;           /* console结构体 */
      #ifdef CONFIG_SERIAL_CORE_CONSOLE
          unsigned long         sysrq;           /* sysrq timeout */
      #endif

      upf_t                 flags;

      #define UPF_FOURPORT         ((__force upf_t) (1 << 1))
      #define UPF_SAK              ((__force upf_t) (1 << 2))
      #define UPF_SPD_MASK         ((__force upf_t) (0x1030))
      #define UPF_SPD_HI           ((__force upf_t) (0x0010))
      #define UPF_SPD_VHI          ((__force upf_t) (0x0020))
      #define UPF_SPD_CUST         ((__force upf_t) (0x0030))
      #define UPF_SPD_SHI          ((__force upf_t) (0x1000))
      #define UPF_SPD_WARP         ((__force upf_t) (0x1010))
      #define UPF_SKIP_TEST        ((__force upf_t) (1 << 6))
      #define UPF_AUTO_IRQ         ((__force upf_t) (1 << 7))
      #define UPF_HARDPPS_CD       ((__force upf_t) (1 << 11))
      #define UPF_LOW_LATENCY      ((__force upf_t) (1 << 13))
      #define UPF_BUGGY_UART       ((__force upf_t) (1 << 14))
      #define UPF_MAGIC_MULTIPLIER ((__force upf_t) (1 << 16))
      #define UPF_CONS_FLOW        ((__force upf_t) (1 << 23))
      #define UPF_SHARE_IRQ        ((__force upf_t) (1 << 24))
      #define UPF_BOOT_AUTOCONF    ((__force upf_t) (1 << 28))
      #define UPF_FIXED_PORT       ((__force upf_t) (1 << 29))
      #define UPF_DEAD             ((__force upf_t) (1 << 30))
      #define UPF_IOREMAP          ((__force upf_t) (1 << 31))

      #define UPF_CHANGE_MASK      ((__force upf_t) (0x17fff))
      #define UPF_USR_MASK         ((__force upf_t) (UPF_SPD_MASK|UPF_LOW_LATENCY))

      unsigned int             mctrl;        /* 当前的moden设置 */
      unsigned int             timeout;      /* character-based timeout */        
      unsigned int             type;         /* 端口类型 */
      const struct uart_ops   *ops;          /* 串口端口操作函数集 */
      unsigned int             custom_divisor;
      unsigned int             line;         /* 端口索引 uart_driver.dev_name加上line组成串口的设备节点的名字 */
      resource_size_t          mapbase;      /* IO内存物理基地址，可用于ioremap */
      struct device           *dev;          /* 父设备 */
      unsigned char            hub6;         /* this should be in the 8250 driver */
      unsigned char            suspended;
      unsigned char            unused[2];
      void                    *private_data; /* 端口私有数据,一般为platform数据指针 */
    };
    • 每一个uart_port对应一个串口设备，uart_port通过uart_add_port添加到uart_state->port数组中去，此结构体中最重要的成员变量是uart_ops,uart操作函数集

  • struct uart_ops

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    /*
     * This structure describes all the operations that can be
    * done on the physical hardware.
    */
    struct uart_ops {
      unsigned int (*tx_empty)(struct uart_port *); /* 串口的Tx FIFO缓存是否为空。如果为空，函数应返回TIOCSER_TEMT，否则返回0。如果端口不支持此操作，返回TIOCSER_TEMT。*/
      void         (*set_mctrl)(struct uart_port *, unsigned int mctrl); /* 设置串口modem控制 */
      unsigned int (*get_mctrl)(struct uart_port *); /* 获取串口modem控制 */
      void         (*stop_tx)(struct uart_port *); /* 禁止串口发送数据 */
      void         (*start_tx)(struct uart_port *); /* 使能串口发送数据 */
      void         (*send_xchar)(struct uart_port *, char ch);/* 发送xChar */
      void         (*stop_rx)(struct uart_port *); /* 禁止串口接收数据 */
      void         (*enable_ms)(struct uart_port *); /* 使能modem的状态信号 */
      void         (*break_ctl)(struct uart_port *, int ctl); /* 设置break信号 */
      int          (*startup)(struct uart_port *); /* 启动串口,应用程序打开串口设备文件时,该函数会被调用 */
      void         (*shutdown)(struct uart_port *); /* 关闭串口,应用程序关闭串口设备文件时,该函数会被调用 */
      void         (*set_termios)(struct uart_port *, struct ktermios *new, struct ktermios *old); /* 设置串口参数 */
      void         (*pm)(struct uart_port *, unsigned int state,
               unsigned int oldstate); /* 串口电源管理 */
      int          (*set_wake)(struct uart_port *, unsigned int state); /*  */
      const char  *(*type)(struct uart_port *); /* 返回一描述串口类型的字符串 */
      void         (*release_port)(struct uart_port *); /* 释放串口已申请的IO端口/IO内存资源,必要时还需iounmap */
      int          (*request_port)(struct uart_port *); /* 申请必要的IO端口/IO内存资源,必要时还可以重新映射串口端口 */
      void         (*config_port)(struct uart_port *, int); /* 执行串口所需的自动配置 */
      int          (*verify_port)(struct uart_port *, struct serial_struct *); /* 核实新串口的信息 */
      int          (*ioctl)(struct uart_port *, unsigned int, unsigned long); /* IO控制 */
    };

  • tty_driver是在register过程中构建的

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    struct tty_driver {
      int     magic;          /* magic number for this structure */
      struct kref kref;       /* Reference management */
      struct cdev **cdevs;
      struct module   *owner;
      const char      *driver_name;
      const char      *name;
      int     name_base;      /* offset of printed name */
      int     major;          /* major device number */
      int     minor_start;    /* start of minor device number */
      unsigned int    num;    /* number of devices allocated */
      short   type;           /* type of tty driver */
      short   subtype;        /* subtype of tty driver */
      struct ktermios init_termios; /* Initial termios */
      unsigned long   flags;          /* tty driver flags */
      struct proc_dir_entry *proc_entry; /* /proc fs entry */
      struct tty_driver *other; /* only used for the PTY driver */

      //Pointer to the tty data structures
      struct tty_struct **ttys;
      struct tty_port **ports;
      struct ktermios **termios;
      void *driver_state;

      //Driver methods
      const struct tty_operations *ops;
      struct list_head tty_drivers;
    }
    • tty_operations提供操作函数，供用户空间调用
    • 将tty_driver构建完成后 通过tty_regoster_driver注册到tty_core中
Linux > Drivers
linux tty 串口驱动
http://example.com/2022/11/27/linux tty串口驱动/
作者
Hector
发布于
2022年11月27日
许可协议